1. Field of the Invention
This invention relates to a surgical rotary bone reamer. More specifically this invention relates to a rotary intramedullary reamer for long bones.
2. Description of the Prior Art
Many fractures of long bones can be stabilized satisfactorily by surgically inserting a shaft, rod or nail down the intramedullary canal of the bone. Since the natural canal is irregular in internal diameter from end to end and since all intramedullary fixation devices gain strength with increases in diameter, most surgical procedures call for incremental reaming. Typically, reamers with 0.5 mm or 1.0 mm increases in outside diameters are used sequentially.
Conventional intramedullary reamers are bullet-shaped, i.e. cylinder with a hemisphere end; and have multiple teeth on their surface. These teeth may be oriented with the long axis of the reamer or at a slight angle thereto. The teeth are generally shallow and give the conventional device the appearance resembling a rotary file. The reamer end may be fixed to a solid shaft or a flexible shaft. The shape of reamers may vary from that described above to that of a sphere or to an acorn shape. Furthermore, the shaft and reamer head may have an axial channel or hole. The shallow teeth produce coarse particulate cutting chips which stay in the valleys between the teeth to clog the reamer head so that it fails to progress. As a result, the reamer must be laboriously cleaned only to be rapidly clogged again.
In addition, in the conventional reamer, the cutting edges cannot be sharpened without altering the outside diameter thereof and therefore ruining the same. To incur less expense, dull ineffective reamers are often retained and used.
Some conventional reamers are not well guided by the wall of the intramedullary canal of long bones and can cut through the wall of the bones.
U.S. Pat. No. 3,633,583 discloses a surgical rotary bone cutter having substantially the shape of a hemisphere and a diametrical slot into which a single flat blade can be positioned. A channel for conveying cutting from the shearing edges is formed in the head alongside each shear edge.
U.S. Pat. No. 3,409,965 describes a tipped cutting tool having a cylindrical body and a ball end provided with diametrical slots. A strip of cutting material is formed into U shape and brazed in the slot to form cutting edges at opposite sides and across the end of the body.
U.S. Pat. No. 1,296,549 discloses a cutting tool comprising a body member with its lateral and forward edges provided with grooves formed in the opposite edges thereof and cutting tips filling said grooves.
U.S. Pat. Nos. 3,630,204 and 3,702,611 disclose surgical reamers having a hemispherical head. Both reamers are designed for forming a hemispherical socket in a bone, e.g. in hip surgery.
U.S. Pat. No. 2,811,187 teaches a dovetail counter-sinking tool in which the tool shaft has a slot in which are secured a pair of pivotal blades.
U.S. Pat. No. 3,554,192 discloses a medullary space drill having a flexible shaft. A drill head is welded and soldered to one end of the shaft whereas the other end is connected to a rotary driver means. The shaft comprises a plurality of parallel flexible elements which are arranged to provide a central passage for receiving an elongated guide element.
None of the above-listed patents discloses a reamer which has a replaceable blade similar to that of the instant invention.